Locomotive engine control systems can be configured to optimize engine performance parameters to improve fuel economy and reduce greenhouse gas emissions. However, optimizations focusing on fuel economy can lead to elevated NOx levels. At the same time, stringent government regulations require NOx emissions to be maintained within a threshold. Optimization routines configured to reduce exhaust NOx levels can lead to a drop in fuel economy and elevated CO2, and other greenhouse gas, emissions. In other words, trade-offs between NOx emissions and fuel economy may be challenging.